Latitude:
/^(\+|-)?(?:90(?:(?:\.0{1,6})?)|(?:[0-9]|[1-8][0-9])(?:(?:\.[0-9]{1,12})?))$/
Longitude:
/^(\+|-)?(?:180(?:(?:\.0{1,6})?)|(?:[0-9]|[1-9][0-9]|1[0-7][0-9])(?:(?:\.[0-9]{1,12})?))$/
Example:
$lat_pattern = '/^(\+|-)?(?:90(?:(?:\.0{1,6})?)|(?:[0-9]|[1-8][0-9])(?:(?:\.[0-9]{1,12})?))$/';
$lng_pattern = '/^(\+|-)?(?:180(?:(?:\.0{1,6})?)|(?:[0-9]|[1-9][0-9]|1[0-7][0-9])(?:(?:\.[0-9]{1,12})?))$/';
if (!preg_match($lat_pattern, $latitude) || !preg_match($lng_pattern, $longitude)) {
echo "Latitude or longitude is not correctly formatted";
}